A Crossed Module giving the Godbillon-Vey Cocycle
arXiv:math-ph/0003034
Abstract
We find crossed modules, i.e. certain 4 term exact sequences, associated to the Godbillon-Vey class for W_1, Vect(S^1), Vect_{1,0}(Σ) and Hol(Σ_r), i.e. for the Lie algebras of formal vector fields in 1 variable, vector fields on the circle, differentiable vector fields of holomorphic type on a Riemann surface and holomorphic vector fields on an open Riemann surface.
6 pages, submitted to Lett. Mth. Phys, we added reference [6]